


Metamorphosis

by panda_shi



Category: Naruto
Genre: Alternate Universe - Canon Divergence, Anbu Yamato | Tenzou, Body Horror, Body Image, Body Modification, DNA alteration, Evolution, Explicit Sexual Content, Graphic Description, Human Experimentation, Idiots in Love, Love, M/M, Metamorphosis, Poisoning, Post-Naruto Time Skip | Naruto Shippuden, Science Experiments, Sexual Content, Snake DNA, Unethical Experimentation, Yamato | Tenzou Snake, snake sex
Language: English
Status: Completed
Published: 2020-12-21
Updated: 2020-12-21
Packaged: 2021-03-10 23:48:21
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 4,975
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/28215726
Author URL: https://archiveofourown.org/users/panda_shi/pseuds/panda_shi
Summary: It starts with a bad rash, a little after Tenzou turns thirty.Iruka notices it when Tenzou would scratch at underside of his arm, not intentionally, but furiously. He does it without thinking too, Iruka notices. Tenzou does it when he’s watching television, sometimes in the middle of dinner, sometimes right after a shower, too.
Relationships: Umino Iruka/Yamato | Tenzou
Comments: 6
Kudos: 32





	Metamorphosis

**Author's Note:**

> Self beta'd. Born from a conversation in Discord: Tenzou's Cabin channel. Because why not. Also inspired by (tumblr: @kisudoodles) art on Snek-Tenzou!
> 
> **Please, please mind the tags.**

It starts with a bad rash, a little after Tenzou turns thirty.

Iruka notices it when Tenzou would scratch at underside of his arm, not intentionally, but furiously. He does it without thinking too, Iruka notices. Tenzou does it when he’s watching television, sometimes in the middle of dinner, sometimes right after a shower, too.

The rash spreads, red and angry, the skin breaking and looking dry, bits and pieces of skin peeling. Tenzou does it too around the sides of his body, sometimes using a clone to get to a stubborn area near his shoulder blades. It spreads downwards like a bad allergy, skin drying down the length of his outer thigh, angry red scratch lines that a week into it, Iruka is actively slapping Tenzou’s hand away each time he sees Tenzou scratching like a rabid dog with a bad onset of fleas.

A regime of rigorous moisturizing is set. Tenzou slathers the itch with medical grade creams, takes his anti-histamine religiously as prescribed by a medic when he finally caved and went about seeing one.

It does nothing to make the itching stop.

Until one day in the middle of dinner, Tenzou stops mid-scratch and goes eerily still.

It is then that Iruka watches, with horror in his gaze matching that of Tenzou’s as Tenzou stares at his triceps, his fingernails caught in what looks like a patch of skin, something that pulls away with a sickening crackling noise. Iruka watches with his breath stuck in his throat, as Tenzou stares at his arm, lips twisted in disgust, mortification and utter horror as he peels off the outer layer of his skin, like duct tape being ripped of a cardboard box, old skin coming off like cobwebs being tugged and unraveled. Iruka watches, his dinner roiling in his stomach, as Tenzou’s skin continues to come off, all the way up the curve of his shoulders, and down the line of his collarbone, where it _rips_ off just from under Tenzou’s right ear. Tenzou who is breathing hard, whose eyes are straining towards the outer corners of his eyelids, pupils blown wide as he peels and peels, all the way up the curve of his neck where the skin is angry red and flaky.

Tenzou holds out what looks like a big part of him in his hand, under the halogen light illuminating over their kitchen table, the large piece of skin that looks white and semi transparent, lined with what looks like scales. It _trembles_ in Tenzou’s white knuckled grip, violent and so unsteady, so unlike Tenzou who is one of the strongest, if not steadiest men Iruka knows. Which sure enough, there, on the length of his upper arm and the curve of his shoulder, under the newly paled skin is something darker, something with a glossy sheen, reptilian in nature, a darkened black sheen fused into Tenzou’s smooth skin, scales that is defined in white, glossy under the halogen line, the jet black surface of each unbroken sheath of scales silky smooth and just underneath it, if one looked closely, there is a kaleidoscope glow of dark, rich indigo. 

The chopsticks in Iruka’s hands clatters somewhere over his rice bowl and down to the floor, the sound of it falling slicing through the shocked silence of their home.

Tenzou goes ashy white, his breath staggering out of his lungs in what looks like an open display of panic.

And then Tenzou is turning to his side, the piece of skin in his hand falling on the tiled floors as Tenzou heaves out his dinner and stomach acid, the sound of retching splattering over the tiled, rancid and sick.

Iruka jolts out from his shock, is on his feet and next to his partner, his fingers pressing over the cold scales that is so eerily like a black cobra, icy under his fingertips. Foreign. Strange. He has to _tear_ his gaze away from it, as he carefully helps Tenzou who continues to empty his stomach, shaking under Iruka’s hold, afraid and so very terrified, so very vulnerable all of a sudden, that Iruka can do nothing but wipe the corners of his lover’s mouth with a paper towel, holds Tenzou’s gaze and say:

“You’re going to be fine.”

*

 _You’re going to be fine_ , turns out to be Iruka’s biggest lie.

*

Iruka finds Tenzou one day, seated on the toilet seat lid naked, damp from a shower, containers of moisturising cream scattered about on the floor, spilling into the tiles, a kunai in his trembling hand. A kunai that Tenzou digs into his outer thigh, forcing the itchy, chalky white surface of his skin to peel off, ripping it off his leg and dumping it on what looks like a small pile of yellowed almost opague dried skin on the tiles. Iruka watches with his stomach turning, as Tenzou grunts and _rips_ skin of his thighs, like how one would peel dried plaster.

It makes a sickening sound, something that Iruka doesn’t think he will forget, when huge clumps of skin being pulled with that gooesbumps inducing, ripping sound drills into his ears. Tenzou`s harsh breathing and grunts cuts through the pin drop silence of the bathroom, the loudness of it bouncing off the tiled walls. Iruka watches helplessly, his knees weak as he leans against the doorframe, how Tenzou catches a bit of skin on the tip of the kunai, holding the blade the way one would when they’re about peel fruit, digging the blade into himself and peeling dry skin off.

It unfurls like apple peal, the length coiling and twisting as it dangles past Tenzou’s thigh, severing when Tenzou _yanks_ at it sharply after looping the length of it around his fist.

Iruka watches as Tenzou _grits_ his teeth, hissing through it, eyes scrunching shut when he presses shaking hands to the exposed new skin, jet black, like the ones that decorate the underside of his arms, feathering up over curve of his bicep, over his collarbone and up the sides of his neck to taper off somewhere behind his ear.

Now the scales lines his outer thigh, the lean cut of his muscle calves. It fades to Tenzou’s real skin somewhere at his heels.

The kunai clatters to the ground loudly, jerking Iruka back to reality.

Tenzou is looking up at him, distress all over his face, a film of salt in his eyes as he shakes his head, biting his lower lip as a sound _tears_ past his throat.

Helpless.

Iruka is kneeling before him in a heartbeat, brushing the anguish from under Tenzou’s eyelids, and lying, just lying because what else can he do?

“It’s okay, you’re okay,” Iruka _lies_ , gods, how he fucking _lies_.

Tenzou shakes under his grip, not leaning forward, not touching Iruka; perhaps it’s disgust, perhaps he thinks he’s a monster.

Iruka wraps his arms around his lover all the same, pressing lips over the cold scales at the back of Tenzou’s ear, continuously whispering the heinous lie.

*

Tenzou stops itching a month and a half later.

Tenzou also stops touching Iruka for just about that long.

Tenzou stops eating too, Iruka notices, going on for days at a time in between meals.

Tenzou also comes home one day with a space heater, something he keeps running whenever he’s seated in whatever in the apartment. Tenzou had taken a liking to always wearing full sleeve shirts and pants in the house, never touching his tank tops anymore, never showing parts of him to Iruka anymore.

Iruka realizes that it’s mostly because Tenzou is always cold. He’s always got his arms around himself, trying to keep warm, even when he’s got socks and a sweater on during Konoha’s early fall where the sun still burns quite hot during the peak of the day.

Tenzou is changing. Too fast, too quick, too soon.

And there’s nothing to be done.

*

The worst change, however, Iruka thinks is the fact that Tenzou becomes mostly drawn inwards, unable to quite meet Iruka’s gaze, always keeping it averted, his entire aura shifting to something that is not at all like the man has come to know and love for the past seven years. Tenzou shies _away_ from Iruka, like he’s afraid of being burned, of being judged.

One day, Tenzou _flinches_ when Iruka takes hold of his hand, tremors going through, that it takes great strength that Iruka didn’t realize he had to not just sink to his knees and weep at being pushed away like this because this, Tenzou not trusting him with _this_ – whatever the _fuck_ this is – Tenzou too afraid of what’s happening that he forgets Iruka loves the man under the mask, not the monster that mask represents.

How is this any different?

How is having scales that look like it belongs to a snake than that of a man be any different from the white porcelain mask Tenzou is known for?

“You are still my greatest joy,” Iruka says, the breath wedged somewhere in his throat, as he releases his hold on Tenzou’s hand and cups his handsome face in his palms. “That hasn’t changed, Tenzou. Even when parts of you have.”

“Don’t be too hasty with your judgment, Iruka-sensei,” Tenzou says, eyes cast downwards, as he reaches up and tugs Iruka’s hands off his face. “I have a feeling this is far from over.”

(That more than anything, breaks faster than any s-class justu ever could.)

*

Tenzou spends a lot of time being observed by Tsunade, the attribute changes to his form rendering him under village arrest until they can prove that he isn’t in any danger to himself.

(That he isn’t a threat to the village.)

They find trace DNA of king cobra in his bloodstream, alongside black mamba and the reticulated python.

Tenzou doesn’t tell Iruka.

He shows him, weeks later.

He wordlessly comes home one day with his prognosis, hands the thick report that Tsunade, Sakura and Konoha’s team of geneticists has put together and says nothing.

Iruka reads it as every part of him skids to a stop and also says nothing.

Not when Tenzou walks away to their bedroom, his shoulders slouched, heavy with the weight of the world, the sins of a traitor weighing him down, evidence of his inhumane experiments decorating Tenzou’s naked body like tattoos as he changes out of his uniform. When words like experiment, DNA fusion, DNA restructure and a slew of other terms that Iruka isn’t medically equipped to comprehend; he just understands that Tenzou is changing, that this may be the last of it, or not. That his chakra pathways have changed, is now sub-human, that it resembles more of a cross between human and snake and a whisper of the Shodaime’s, too. That this may hinder his ability, that he should observe caution and report any changes at once.

And somewhere in there, is an order issued by the Rokudaime that Tenzou has agreed to. The order is to have a security detail constantly on guard, or on watch.

Iruka drops the report from limp hands on the table, looking out the window of their serene apartment where surely, ANBU must keeping watch. Or hunters.

The report on the table, Iruka decides is something he doesn’t give two shits about.

He decides then and there, as he crosses the space between himself and Tenzou that just because Tenzou is evolving, it doesn’t mean he loves Tenzou less. Iruka grabs Tenzou by the wrist, spins him with a demanding yank and pulls Tenzou in for a kiss, uncaring that Tenzou goes still in his arms, _frozen_.

Only to circle his arms Iruka in what can only be a desperate hold, like Iruka is Tenzou’s only anchor in this metamorphosing storm. Tenzou’s hands are cold, _gods_ , they’re so, so cold, ice on the feverish heat that ignites on Iruka’s skin, as they kiss and fall into bed. Iruka shudders when scales brushes against his thighs, when his fingers trace the ridges and dips of the scales on Tenzou’s neck, shoulders and arms, their breaths crashing Iruka closes his eyes when Tenzou’s fingers press against his entrance, just as Iruka’s fingers fists into Tenzou’s hair.

It’s when he sees it, as Tenzou pushes his cock into his body, how Tenzou’s pupil is no longer round but slitted, cutting down the wondrously beautiful dark iris, _eerie_ and focused, dilated in focus. Gold lines the outer pupil, as bright as daffodils in the summer time, tapering off to Tenzou’s iris that still gleams like black diamonds in the dark.

Iruka thinks it’s beautiful, as the breath gets knocked out of him when Tenzou fills him with his cock, thick, gods, _so,_ so thick _,_ and so long, too much, suddenly just too much, that Iruka can’t help himself when he comes too soon, too quick, too depraved of Tenzou in the past several weeks when parts of Tenzou had been itching and peeling. Iruka forgets how big Tenzou is, how he seems to so easily fill him up too quick, gods, was he always this big?

Tenzou has his forehead on Iruka’s chest, bowed over his body like Iruka is a god in a temple, shaking under the ferocity of his orgasm that had flooded Iruka with so much heat, he can feel the cum trickling past the cock that is still in his body, unable to stay in him anymore.

Iruka cups Tenzou’s face, tugging him up, one hand languidly brushing over the black scales on Tenzou’s arm.

“I think you’re beautiful, Tenzou…” Iruka says, whisper-soft, one hand brushing over Tenzou’s eyebrow, tracing down over his lashes to rest on Tenzou’s cheekbone, Iruka losing himself in the black and gold depths. “You’ll keep me nice and cool even with the heater on. I’ve noticed how you’re always cold…”

Tenzou bites his lower lip, dropping his gaze away from Iruka again, gravel in his voice when he asks, “How can you say that?”

“Because it’s the truth,” Iruka says.

And this time, it isn’t a lie at all.

*

The next morning, Tenzou notices the change in his irises when he’s brushing his teeth. Iruka is there when the motion of brushing stops and the toothbrush clatters to the sink from limp fingers.

Iruka is there, putting himself between the mirror and Tenzou, pressing lips to Tenzou’s chin.

“Gives you a bit of a legendary vibe, if you ask me,” Iruka murmurs, pushing damp hair strands off Tenzou’s face. “Kind of badass. I want you fuck me, while looking at me like that…”

“R-Really?”

“Yes.” Iruka presses their forehead together, inhaling the deep scent of cedar trees and amber and just something a little cooler. New. “ _Really_.”

Tenzou hesitates.

That hesitation fades when Iruka tilts his head and leans up for a kiss.

*

“You know, this might just be my favorite change yet,” Iruka says, after he pulls his mouth of Tenzou’s cock with a loud, wet, lewd pop and stares at the hardened length of it.

“You know they’re watching us now, right?” Tenzou says, a little breathless from his perch on the single seater sofa, arms hanging off the armrest, neck flushed, his cock jutting up to his abdomen, thicker, longer and just a bit fuller than what Iruka remembers.

“Let them know that I have Konoha’s greatest cock; all of it mine,” Iruka _grins_ , something that makes Tenzou groan in his throat as he tilts his head back and grits his teeth, when Iruka lewdly traces the tip of his cock to catch the beading pre-cum with the tip of his tongue.

“ _Iruka_ …”

“I’d thank Orochimaru for this. Maybe even send him a fruit basket. You know, like the ones with the fancy bows and stuff?” Iruka reaches up cups Tenzou’s balls in his palms, rolling them gently, relishing the sound of Tenzou exhaling through his teeth. “He gave you a bigger dick. Not that you weren’t big enough before.”

“Sounds like you the only thing you’re happy with is my cock, like my old one wasn’t good enough,” Tenzou grunts, his fingers snapping to the armrest when Iruka grabs the twitching length and _squeezes_.

“Don’t put words in my mouth,” Iruka warns with an unimpressed tilt of his head. “But this is the new you now. And I’m embracing every inch of it, whether it’s permanent or if Tsunade and Sakura manages to find a way to reverse it, which judging from the studies so far, seems to not be the fact.”

Iruka gives the throbbing length one long, slow, languid stroke, leaving Tenzou shuddering in the wake of his hand’s ministrations.

“Right...”

“Tenzou,” Iruka says, waiting for Tenzou to focus his gaze on him. “I want you to come on my face.”

It’s all the instruction Tenzou seems to need, as he pushes his hard cock back into Iruka’s pliant mouth, fucking the breath out of Iruka until he comes hot and thick all over Iruka’s face.

*

Tenzou confirms that he’s faster.

That he’s stronger.

That his chakra reserves, if anything, have easily doubled.

That he’s working on learning what else has changed about his abilities, which doesn’t seem to be much save for the added strength, speed and chakra. The positive effects of the change seem to bolster Tenzou’s confidence, because he says one night, while lying in bed, “This will be useful during long missions.”

Iruka cannot help but agree.

*

For a moment, things seems to have gone back to normal. Save for the fact that Tenzou seems to be a lot stronger, with more strength in his grip than he did before, Iruka thinks they’ve moved past the initial and most difficult hurdle of Tenzou’s metamorphosis.

That is, until one night, while Iruka straddles Tenzou’s lap and starts to kiss him, pushing him down the pillows, he finds himself suddenly looking up at the ceiling, Tenzou leaving nips and bites under his ear and down the length of his neck, their arousals rubbing against each other, ready and full, it just happens.

Tenzou bites Iruka hard enough to break skin and mark, leaving Iruka gasping for breath that he suddenly can’t quite take anymore.

What starts of sensual gripping ebs away to panic when Iruka realizes that he can’t breathe, that his lungs seems to have stopped functioning under his ribs. His hands that had been gripping Tenzou in his air scrambles down his arm, fighting him, one hand coming up to his throat as Iruka chokes on his own tongue, his body suddenly going cold, every part of his shaking, shaking, _shaking_ as his entire body goes into anaphylactic shock.

Cold sweat starts to form on his skin, his breath coming out rapid and shallow, his entire world swimming as the ceiling that should be above him start to fall and tip over dangerously to his right, blurring to a mess when Iruka fights to keep his eyes open, trying to tell Tenzou he’s okay, he’s fine, really, he’s _fine_.

Except Tenzou isn’t listening to him.

Tenzou isn’t listening because Tenzou is wrapping him in a blanket and rushing him to the emergency where the last Iruka sees is Tenzou’s terrified face, the sharp fangs that has now replaced his incisors and the passing halogen lights of the hospital ceiling.

*

Iruka comes to in a small recovery room, waking up with a sharp gasp that mists the oxygen mask covering his nose and mouth.

Tenzou is beside him immediately, his pallor waxy, eyes red rimmed and shame painting his face. Iruka can only grin up at him, reaching up tiredly, weakly, to tug the oxygen mask off to ask, “Poison?”

Tenzou swallows and nods. “Yes.”

“Figures,” Iruka sighs, slumping heavily on the pillow. “No more biting for you then.”

“Iruka—“

“Please don’t go back to avoiding me, not touching me like before. Not _that_ ,” Iruka says, his voice cracking. “Anything but _that_.”

“I almost killed you,” Tenzou warns, dropping to his knees on the floor, pressing his forehead on Iruka’s cold hand. “ _I almost killed you_.”

“But you didn’t,” Iruka reasons, sitting up straight. “You _didn’t_. And you _won’t_. You’ll learn to control and use this too, like your speed, your strength and your added chakra reserve. This too, will be deadly in the field.”

“ _And you!_ ” Tenzou snaps, loud, biting, his new sharp teeth gleaming under the halogen light. “ _Look at me, Iruka!”_

“I am…” Iruka says softly, watching as the tears of frustration, guilt and fear gathers around the corners of Tenzou’s eyes. “I am looking at you...”

“You nearly _died_! I could have lost you tonight! Are you just incapable of wrapping your head around that? Or are you just headstrong about denying this new reality all together?” Tenzou demands, trying to shake reason into Iruka, his jaw pulled taut, veins around his neck protruding from the urge to just want to scream and yell and break things because this isn’t right. None of this is right.

“It means I love you, still,” Iruka says. “It means I don’t blame you. I forgive you. And that I have more of you to love than before…” Iruka reaches out and brushes fingers over the tears that are carving down Tenzou’s cheeks, cold and crystalline. “I am not leaving you. I’m going to have to die first before that can happen.”

Tenzou exhales a _sound_ that sounds so unlike him, so raw, like a wounded animal as he buries his forehead on the hospital mattress, holding Iruka’s hand to his cheek and weeps.

*

Iruka comes home to several full blooms of yellow roses growing on one side of their garden.

Yellow roses – Tenzou’s eternal apology.

*

Further study shows that the Tenzou develops poisonous glands at the roof of his mouth, one that is connected to new glands that sits just above the lymph nods on his neck. A controlled environment experiment also proves that Tenzou is now capable of a bite force that is roughly about 12,000 newton, just shy of a saltwater crocodile’s biting power. Tenzou’s bone structure seems to be different now too, especially around his spine and skull to accommodate the new strength that had left the geneticists, Sakura and Tsunade utterly speechless.

The venom, it seems, is a muscle that Tenzou can control.

It takes weeks to flex it, with Tenzou spraying venom all over the tiled laboratory study room behind glass like a lab rat being observed for several weeks before he figures out the finer motor control behind it.

It’s like flexing his fingers, except this is somewhere in his throat.

When it’s relaxed, the poison, according to the x-ray, is contained within its glands.

When Tenzou contracts, the will to attack flaring and triggering his fight response, the glands contracts before they flare wide open, pushing streams of copious amount of poison that is chemical mix of proteses, hyaluronidase, phosphatase, phospholipase and neurotoxic peptides, cytotoxins that depending on the bite and amount of venom injected into the victim, can cause necrosis, respiratory failure, hypolocomation, hyperalgesia, cardiovascular collapse, paralysis and death anywhere between, apparently, fifteen minutes to a few hours.

They tell him it’s the combine DNA of both king cobra and black mamba, that it is a complex concoction that seemed to have given birth to what looks like a new specie of snake all together. That there isn’t anything like it anywhere.

This also gets explained to Iruka in a cold, reporting, disconnected tone.

Something that Iruka takes in stride, smiles and simply takes Tenzou’s hand and says, “If I were your enemy, I would never want to piss you off. I’d be so _screwed_ , it’s not even funny.”

*

It is winter, approximately four months since the change had initially started, in the middle of training with Kakashi when it happens.

In an effort to evade and strike faster, Tenzou’s fight response seemed to have triggered something in his body that makes him burrow in the ground and his body shift and change the way it does when he wants to grow parts of mokuton out of him.

Except instead of mokuton, Tenzou’s lower half of his body changes to a thirteen feet black snake, the length of his body propelling forward before end of his tail slams Kakashi sideways, sending him flying across the trees and deeper into the forest, past the training ground they are currently using.

Tenzou remains there, towering above the ground than his usual height, watching with wide eyes as he stares at his hands, at the length of his smooth, cool tail that coils around in the ground when he lowers himself, thinks of lowering himself, just as Kakashi coughs and sputters out of the tree line only to come to skidding halt at the sight Tenzou makes.

“Well, that’s unexpected,” Kakashi glibly says, landing on his ass. “ _Wow_.”

“Y-Yeah…” Tenzou says, flicking his tail. It’s like moving another limb. “S-Senpai, I – I don’t know how to change back.”

Kakashi nods dumbly, blinking. “We’ll figure it out…”  
  
*

 _We’ll figure out_ turns out to be easier said than done.

Tenzou goes home under a guise of genjutsu, shoving his entire length into the bathtub to wash himself while Kakashi sits mutely in the living room. Tenzou joins him after using two towels to dry himself off, standing there in a full sleeved shird with his snake half coiled as he sits on the black vaguely patterned scales with his arms crossed deep in thought, trying to figure out how to change back, if it’s like a henge or if it’s a muscle flex of sorts like his venomous glands.

It is exactly that kind of picture Iruka comes home to, where the satchel strap on his shoulder drops to the ground in mute shock.

“It happened by accident,” Kakashi offers, when Tenzou suddenly fails at forming words, looking ashamed and mortified.

“Oh.” Iruka picks up his satchel and sets it properly on the sofa, moving past Kakashi to press a proper I’m-home kiss on Tenzou’s lips. “I’ll start dinner, then, while you two figure that out. Please stay, Kakashi-san. I insist.”

*

That night, getting into bed proves to be a challenge. Tenzou’s tail is so long that it ends up hanging off across one side of the bed.

“I know you’re always cold,” Iruka says, placing his cheek on Tenzou’s chest. “But parts of you are still you and so warm, still.”

“You’re warm,” Tenzou says, wrapping his arms tighter around Iruka. “You’re just always warm.”

“Hmmm,” Iruka hums, closing his eyes and giving in to the fatigue of the day. “I know you’re worried. But this too, like the poison, must just be another muscle flex you need to figure out. Just like what Kakashi said easier. You have his support, mine, a team of professionals and team seven. I hope you don’t forget that. We’re in this with you.”

“What if I don’t change back, though?” Tenzou says, reaching down to grasp Iruka’s chin. “I’ll continue to serve the village, yes, but you – how can you choose a life with a creature like me? Look at me. I’m barely human as it is…”

“But you’re still _you_ ,” Iruka answers, tilting his head. “Even if this is permanent, I wouldn’t want to lose _you_ , Tenzou. I’m with you not because of how you _look_. That was never the reason… you shouldn’t forget that.”

Tenzou lifts his tail, Iruka’s eyes trailing down towards it. “My dick is gone.”

“Ah, yes,” Iruka _sighs_ theatrically. “Oh, woe is me and you. Farewell, beloved dick. Hello, thicker tail.”

That leaves Tenzou blinking and Iruka laughing to the point of breathlessness.

*

The changes seem to stop and not develop further after Tenzou’s tongue finally splits one day into what is now a forked tongue. Tenzou just wakes up like that, the appendage divided into two right down the middle. Iruka thinks it doesn’t matter anymore, if Tenzou changes further or not.

Not when they’re in the tub, and Tenzou has the length of his lower body wrapped around Iruka’s middle, suspending him above the said tub, holding him up, as Iruka keeps himself braised around Tenzou’s shoulders, kissing Tenzou and his wicked forked tongue. It doesn’t matter when the tip of Tenzou’s tail brushes around Iruka’s slick entrance, pushing past it and fucks him with it.

It doesn’t even matter when they letter learn that Tenzou’s tail is where his new dick is, two of them, in what Iruka later learns, when he finally picks up a reference book on snakes from the library, is something called hemipenes. It spikes out Tenzou’s tail, two heads, when Tenzou is aroused, pushing outwards and into Iruka that leaves Tenzou tilting his head back when he orgasms, open mouth, _loud_ , his breath harsh, the ferocity of it, apparently, far too much to keep silent anymore.

It’s an oddity, that’s for sure.

It takes adjustment and flexibility, that goes without being said.

But at the end of it all, despite the physical changes, it is still Tenzou’s arms that holds Iruka at night. It is still his lips that whispers good morning against Irukas temples, still the tenor of his voice and the sound of his strong heartbeat that Iruka falls asleep to and wakes up to every single day.

Tenzou figures it out, how to change forms, of course, weeks into his training with Kakashi.

A year later and Tenzou isn’t curling in on himself in embarrassment, but rather wears his scales proudly each time he straps on the ANBU uniform.

And sometimes, when Iruka is feeling a little feisty, he’d whisper, “Fuck me in your _real_ form, taichou.”

Because this, is who Tenzou is.

It’s in his DNA.

This is what’s real.

The request never comes out as a lie, but something rather revering every single time.

**Author's Note:**

> I imagine Tenzou to have a cocktail of snake DNA as follows: king cobra, reticulated python, black mamba, and just a touch of salt water crocodile.
> 
> Hemipenes is real. I thank Rika for telling me. I just had to.


End file.
